TUNIS, April 13 (Reuters) - A Tunisian military court has ordered the release of ousted autocrat Zine El-Abidine Ben Ali's former interior minister and security chief, who were jailed after the country's 2011 revolution, the government and lawyers said.

The release of security chief Ali Seriati and former interior minister Rafik Bel Haj Kalem, accused of repressing protesters during the uprising, may fuel tensions in a country just in the final stages of democratic transition.

Tunisia has mostly overcome the political instability that followed its revolt, adopting a new constitution and installing a consensus caretaker government that is administrating the country until elections later this year.

But as in other "Arab Spring" nations which ousted long-standing rulers in 2011, debate over the role of former regime officials is a sensitive part of transition in Tunisia, where an Islamist party confronts a mainly secular rival coalition.

"They should be freed in the next few days. This is a blow to the transition after the revolution," said Laila Haddad, a lawyer for families of victims who were killed in clashes during the 2011 "Jasmine Revolution" that helped spark the Arab Spring uprisings in Libya, Egypt and Yemen.

The judicial decision late on Saturday night was confirmed by Nizar Ayad, attorney for the former interior minister.

The court ruled the men could be freed after they finished the mandatory three years of their sentences, Haddad said.

A spokesman for Tunisia's presidency called the decision a "shock" for Tunisians, but said the judicial ruling would be respected.

More than 300 people died in the clashes during the protests that were triggered by economic grievances and corruption but quickly spiralled into an uprising against the regime that forced Ben Ali to flee to Saudi Arabia.

A military court sentenced Ben Ali in absentia, and sent the head of his presidential security and his former interior minister to prison for their part in repression.

"This is theatre. We will have our justice in other ways. We will start another revolution," said Ahmed Amri, brother of one of the protesters killed in 2011.

Since Ben Ali's ouster, Tunisia has struggled with a tensions between two main political poles -- the Islamist Ennahda party which won the first free election, and Nidaa Tounes, a coalition led by Ben Ali's former parliament speaker.

Ennahda stepped down at the start of the year under an agreement with its opposition to allow a non-political caretaker government to take over until new elections were held in one of the Arab World's most secular countries.

Tunisia's transition has been seen as a model of compromise and democratic process for a region still in turmoil after the 2011 revolutions that promised new freedoms.

Part of that compromise was an easier acceptance of some ex-Ben Ali officials into politics, unlike Libya and Egypt where former regime figures were initially purged in the early days after the revolutions in those countries. (Writing by Patrick Markey; Editing by Stephen Powell)

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